Amber prep & frcmod files to gromacs

GROMACS version: 2021.5
GROMACS modification: No

Hi all,

I am using amber parameters and have prep and frcmod files for ATP, how would I convert these to rtp files? I tried using acpype, but I would then require mol2 or pdb files, would i have to convert prep and frcmod files to pdb / mol2 first and if so, where would I do that?

I am also using carlson’s modified phosphate parameters and converted the units and such and placed them within the ffnonbonded, bonded.itp and “O3” in the atomtypes files. I converted the dihedral types from kcal to kj and using func 9 such as below. I’m not sure if the negative values from AMBER can also be used in the gromacs form.

O2  P   OS  CT    9       0.0     -1.56000    -3  ; meagher 

I’ve also seen a thread to use http://bugzilla.gromacs.org/issues/721 but unfortunately the link is dead.

Also to note im using the atp.pdb from charmm gui small molecule library . Can i still use this for gromacs pdb2gmx?

Try acpype. See original paper here

Would this be used for the atp.prep file? or would I use a ATP smiles file / ATP pdb from charmm?

Use Antechamber (http://ambermd.org/antechamber/ac.html#antechamber) to convert the prepi file to mol2 and then, use acpype to create gromacs files from the created mol2.

Hello Josh,

Were you able to generate the ATP forcefield from AMBER. Would you kindly share the topology?
regards,
styn

; atp_GMX.itp created by acpype (v: 2022.6.6) on Tue Feb 21 09:07:01 2023

[ atomtypes ]
;name   bond_type     mass     charge   ptype   sigma         epsilon       Amb
 O2       O2          0.00000  0.00000   A     2.95992e-01   8.78640e-01 ; 1.66  0.2100
 P        P           0.00000  0.00000   A     3.74177e-01   8.36800e-01 ; 2.10  0.2000
 OS       OS          0.00000  0.00000   A     3.00001e-01   7.11280e-01 ; 1.68  0.1700
 CT       CT          0.00000  0.00000   A     3.39967e-01   4.57730e-01 ; 1.91  0.1094
 H1       H1          0.00000  0.00000   A     2.47135e-01   6.56888e-02 ; 1.39  0.0157
 H2       H2          0.00000  0.00000   A     2.29317e-01   6.56888e-02 ; 1.29  0.0157
 N*       N*          0.00000  0.00000   A     3.25000e-01   7.11280e-01 ; 1.82  0.1700
 CK       CK          0.00000  0.00000   A     3.39967e-01   3.59824e-01 ; 1.91  0.0860
 H5       H5          0.00000  0.00000   A     2.42146e-01   6.27600e-02 ; 1.36  0.0150
 NB       NB          0.00000  0.00000   A     3.25000e-01   7.11280e-01 ; 1.82  0.1700
 CB       CB          0.00000  0.00000   A     3.39967e-01   3.59824e-01 ; 1.91  0.0860
 CA       CA          0.00000  0.00000   A     3.39967e-01   3.59824e-01 ; 1.91  0.0860
 N2       N2          0.00000  0.00000   A     3.25000e-01   7.11280e-01 ; 1.82  0.1700
 H        H           0.00000  0.00000   A     1.06908e-01   6.56888e-02 ; 0.60  0.0157
 NC       NC          0.00000  0.00000   A     3.25000e-01   7.11280e-01 ; 1.82  0.1700
 CQ       CQ          0.00000  0.00000   A     3.39967e-01   3.59824e-01 ; 1.91  0.0860
 OH       OH          0.00000  0.00000   A     3.06647e-01   8.80314e-01 ; 1.72  0.2104
 HO       HO          0.00000  0.00000   A     0.00000e+00   0.00000e+00 ; 0.00  0.0000

[ moleculetype ]
;name            nrexcl
 atp              3

[ atoms ]
;   nr  type  resi  res  atom  cgnr     charge      mass       ; qtot   bond_type
     1   O2     1   atp   O1G    1    -0.782167     16.00000 ; qtot -0.782
     2    P     1   atp    PG    2     1.514900     30.97000 ; qtot 0.733
     3   O2     1   atp   O2G    3    -0.782167     16.00000 ; qtot -0.049
     4   O2     1   atp   O3G    4    -0.782167     16.00000 ; qtot -0.832
     5   OS     1   atp   O3B    5    -0.840800     16.00000 ; qtot -1.672
     6    P     1   atp    PB    6     1.751801     30.97000 ; qtot 0.079
     7   O2     1   atp   O1B    7    -0.921000     16.00000 ; qtot -0.842
     8   O2     1   atp   O2B    8    -0.921000     16.00000 ; qtot -1.763
     9   OS     1   atp   O3A    9    -0.828800     16.00000 ; qtot -2.591
    10    P     1   atp    PA   10     1.602800     30.97000 ; qtot -0.989
    11   O2     1   atp   O1A   11    -0.895000     16.00000 ; qtot -1.884
    12   O2     1   atp   O2A   12    -0.895000     16.00000 ; qtot -2.779
    13   OS     1   atp   O5*   13    -0.592200     16.00000 ; qtot -3.371
    14   CT     1   atp   C5*   14     0.194400     12.01000 ; qtot -3.176
    15   H1     1   atp   H50   15     0.029200      1.00800 ; qtot -3.147
    16   H1     1   atp   H51   16     0.029200      1.00800 ; qtot -3.118
    17   CT     1   atp   C4*   17     0.081100     12.01000 ; qtot -3.037
    18   H1     1   atp   H40   18     0.071700      1.00800 ; qtot -2.965
    19   OS     1   atp   O4*   19    -0.440600     16.00000 ; qtot -3.406
    20   CT     1   atp   C1*   20     0.241800     12.01000 ; qtot -3.164
    21   H2     1   atp   H10   21     0.044700      1.00800 ; qtot -3.119
    22   N*     1   atp    N9   22    -0.275000     14.01000 ; qtot -3.394
    23   CK     1   atp    C8   23     0.346700     12.01000 ; qtot -3.048
    24   H5     1   atp   H80   24     0.103800      1.00800 ; qtot -2.944
    25   NB     1   atp    N7   25    -0.775100     14.01000 ; qtot -3.719
    26   CB     1   atp    C5   26    -0.110200     12.01000 ; qtot -3.829
    27   CA     1   atp    C6   27     0.524200     12.01000 ; qtot -3.305
    28   N2     1   atp    N6   28    -0.890500     14.01000 ; qtot -4.195
    29    H     1   atp   H60   29     0.348800      1.00800 ; qtot -3.847
    30    H     1   atp   H61   30     0.348800      1.00800 ; qtot -3.498
    31   NC     1   atp    N1   31    -0.781000     14.01000 ; qtot -4.279
    32   CQ     1   atp    C2   32     0.554900     12.01000 ; qtot -3.724
    33   H5     1   atp    H2   33    -0.003900      1.00800 ; qtot -3.728
    34   NC     1   atp    N3   34    -0.706000     14.01000 ; qtot -4.434
    35   CB     1   atp    C4   35     0.386800     12.01000 ; qtot -4.047
    36   CT     1   atp   C3*   36     0.114100     12.01000 ; qtot -3.933
    37   H1     1   atp   H30   37     0.084700      1.00800 ; qtot -3.848
    38   OH     1   atp   O3*   38    -0.678800     16.00000 ; qtot -4.527
    39   HO     1   atp   H3'   39     0.511000      1.00800 ; qtot -4.016
    40   CT     1   atp   C2*   40     0.115100     12.01000 ; qtot -3.901
    41   H1     1   atp   H20   41     0.104700      1.00800 ; qtot -3.796
    42   OH     1   atp   O2*   42    -0.619800     16.00000 ; qtot -4.416
    43   HO     1   atp   H2'   43     0.416000      1.00800 ; qtot -4.000

[ bonds ]
;   ai     aj funct   r             k
     1      2   1    1.4800e-01    4.3932e+05 ;    O1G - PG    
     2      3   1    1.4800e-01    4.3932e+05 ;     PG - O2G   
     2      4   1    1.4800e-01    4.3932e+05 ;     PG - O3G   
     2      5   1    1.6100e-01    1.9246e+05 ;     PG - O3B   
     5      6   1    1.6100e-01    1.9246e+05 ;    O3B - PB    
     6      7   1    1.4800e-01    4.3932e+05 ;     PB - O1B   
     6      8   1    1.4800e-01    4.3932e+05 ;     PB - O2B   
     6      9   1    1.6100e-01    1.9246e+05 ;     PB - O3A   
     9     10   1    1.6100e-01    1.9246e+05 ;    O3A - PA    
    10     11   1    1.4800e-01    4.3932e+05 ;     PA - O1A   
    10     12   1    1.4800e-01    4.3932e+05 ;     PA - O2A   
    10     13   1    1.6100e-01    1.9246e+05 ;     PA - O5*   
    13     14   1    1.4100e-01    2.6778e+05 ;    O5* - C5*   
    14     15   1    1.0900e-01    2.8451e+05 ;    C5* - H50   
    14     16   1    1.0900e-01    2.8451e+05 ;    C5* - H51   
    14     17   1    1.5260e-01    2.5941e+05 ;    C5* - C4*   
    17     18   1    1.0900e-01    2.8451e+05 ;    C4* - H40   
    17     19   1    1.4100e-01    2.6778e+05 ;    C4* - O4*   
    17     36   1    1.5260e-01    2.5941e+05 ;    C4* - C3*   
    19     20   1    1.4100e-01    2.6778e+05 ;    O4* - C1*   
    20     21   1    1.0900e-01    2.8451e+05 ;    C1* - H10   
    20     22   1    1.4750e-01    2.8200e+05 ;    C1* - N9    
    20     40   1    1.5260e-01    2.5941e+05 ;    C1* - C2*   
    22     23   1    1.3710e-01    3.6819e+05 ;     N9 - C8    
    22     35   1    1.3740e-01    3.6484e+05 ;     N9 - C4    
    23     24   1    1.0800e-01    3.0711e+05 ;     C8 - H80   
    23     25   1    1.3040e-01    4.4267e+05 ;     C8 - N7    
    25     26   1    1.3910e-01    3.4644e+05 ;     N7 - C5    
    26     27   1    1.4040e-01    3.9246e+05 ;     C5 - C6    
    26     35   1    1.3700e-01    4.3514e+05 ;     C5 - C4    
    27     28   1    1.3400e-01    4.0250e+05 ;     C6 - N6    
    27     31   1    1.3390e-01    4.0417e+05 ;     C6 - N1    
    28     29   1    1.0100e-01    3.6317e+05 ;     N6 - H60   
    28     30   1    1.0100e-01    3.6317e+05 ;     N6 - H61   
    31     32   1    1.3240e-01    4.2007e+05 ;     N1 - C2    
    32     33   1    1.0800e-01    3.0711e+05 ;     C2 - H2    
    32     34   1    1.3240e-01    4.2007e+05 ;     C2 - N3    
    34     35   1    1.3540e-01    3.8576e+05 ;     N3 - C4    
    36     37   1    1.0900e-01    2.8451e+05 ;    C3* - H30   
    36     38   1    1.4100e-01    2.6778e+05 ;    C3* - O3*   
    36     40   1    1.5260e-01    2.5941e+05 ;    C3* - C2*   
    38     39   1    9.6000e-02    4.6275e+05 ;    O3* - H3'   
    40     41   1    1.0900e-01    2.8451e+05 ;    C2* - H20   
    40     42   1    1.4100e-01    2.6778e+05 ;    C2* - O2*   
    42     43   1    9.6000e-02    4.6275e+05 ;    O2* - H2'   

[ pairs ]
;   ai     aj    funct
     1      6      1 ;    O1G - PB    
     2      7      1 ;     PG - O1B   
     2      8      1 ;     PG - O2B   
     2      9      1 ;     PG - O3A   
     3      6      1 ;    O2G - PB    
     4      6      1 ;    O3G - PB    
     5     10      1 ;    O3B - PA    
     6     11      1 ;     PB - O1A   
     6     12      1 ;     PB - O2A   
     6     13      1 ;     PB - O5*   
     7     10      1 ;    O1B - PA    
     8     10      1 ;    O2B - PA    
     9     14      1 ;    O3A - C5*   
    10     15      1 ;     PA - H50   
    10     16      1 ;     PA - H51   
    10     17      1 ;     PA - C4*   
    11     14      1 ;    O1A - C5*   
    12     14      1 ;    O2A - C5*   
    13     18      1 ;    O5* - H40   
    13     19      1 ;    O5* - O4*   
    13     36      1 ;    O5* - C3*   
    14     20      1 ;    C5* - C1*   
    14     37      1 ;    C5* - H30   
    14     38      1 ;    C5* - O3*   
    14     40      1 ;    C5* - C2*   
    15     18      1 ;    H50 - H40   
    15     19      1 ;    H50 - O4*   
    15     36      1 ;    H50 - C3*   
    16     18      1 ;    H51 - H40   
    16     19      1 ;    H51 - O4*   
    16     36      1 ;    H51 - C3*   
    17     21      1 ;    C4* - H10   
    17     22      1 ;    C4* - N9    
    17     39      1 ;    C4* - H3'   
    17     41      1 ;    C4* - H20   
    17     42      1 ;    C4* - O2*   
    18     20      1 ;    H40 - C1*   
    18     37      1 ;    H40 - H30   
    18     38      1 ;    H40 - O3*   
    18     40      1 ;    H40 - C2*   
    19     23      1 ;    O4* - C8    
    19     35      1 ;    O4* - C4    
    19     37      1 ;    O4* - H30   
    19     38      1 ;    O4* - O3*   
    19     41      1 ;    O4* - H20   
    19     42      1 ;    O4* - O2*   
    20     24      1 ;    C1* - H80   
    20     25      1 ;    C1* - N7    
    20     26      1 ;    C1* - C5    
    20     34      1 ;    C1* - N3    
    20     37      1 ;    C1* - H30   
    20     38      1 ;    C1* - O3*   
    20     43      1 ;    C1* - H2'   
    21     23      1 ;    H10 - C8    
    21     35      1 ;    H10 - C4    
    21     36      1 ;    H10 - C3*   
    21     41      1 ;    H10 - H20   
    21     42      1 ;    H10 - O2*   
    22     27      1 ;     N9 - C6    
    22     32      1 ;     N9 - C2    
    22     36      1 ;     N9 - C3*   
    22     41      1 ;     N9 - H20   
    22     42      1 ;     N9 - O2*   
    23     27      1 ;     C8 - C6    
    23     34      1 ;     C8 - N3    
    23     40      1 ;     C8 - C2*   
    24     26      1 ;    H80 - C5    
    24     35      1 ;    H80 - C4    
    25     28      1 ;     N7 - N6    
    25     31      1 ;     N7 - N1    
    25     34      1 ;     N7 - N3    
    26     29      1 ;     C5 - H60   
    26     30      1 ;     C5 - H61   
    26     32      1 ;     C5 - C2    
    27     33      1 ;     C6 - H2    
    27     34      1 ;     C6 - N3    
    28     32      1 ;     N6 - C2    
    28     35      1 ;     N6 - C4    
    29     31      1 ;    H60 - N1    
    30     31      1 ;    H61 - N1    
    31     35      1 ;     N1 - C4    
    33     35      1 ;     H2 - C4    
    35     40      1 ;     C4 - C2*   
    36     43      1 ;    C3* - H2'   
    37     39      1 ;    H30 - H3'   
    37     41      1 ;    H30 - H20   
    37     42      1 ;    H30 - O2*   
    38     41      1 ;    O3* - H20   
    38     42      1 ;    O3* - O2*   
    39     40      1 ;    H3' - C2*   
    41     43      1 ;    H20 - H2'   

[ angles ]
;   ai     aj     ak    funct   theta         cth
     1      2      3      1    1.1990e+02    1.1715e+03 ;    O1G - PG     - O2G   
     1      2      4      1    1.1990e+02    1.1715e+03 ;    O1G - PG     - O3G   
     1      2      5      1    1.0823e+02    8.3680e+02 ;    O1G - PG     - O3B   
     2      5      6      1    1.2050e+02    8.3680e+02 ;     PG - O3B    - PB    
     3      2      4      1    1.1990e+02    1.1715e+03 ;    O2G - PG     - O3G   
     3      2      5      1    1.0823e+02    8.3680e+02 ;    O2G - PG     - O3B   
     4      2      5      1    1.0823e+02    8.3680e+02 ;    O3G - PG     - O3B   
     5      6      7      1    1.0823e+02    8.3680e+02 ;    O3B - PB     - O1B   
     5      6      8      1    1.0823e+02    8.3680e+02 ;    O3B - PB     - O2B   
     5      6      9      1    1.0260e+02    3.7656e+02 ;    O3B - PB     - O3A   
     6      9     10      1    1.2050e+02    8.3680e+02 ;     PB - O3A    - PA    
     7      6      8      1    1.1990e+02    1.1715e+03 ;    O1B - PB     - O2B   
     7      6      9      1    1.0823e+02    8.3680e+02 ;    O1B - PB     - O3A   
     8      6      9      1    1.0823e+02    8.3680e+02 ;    O2B - PB     - O3A   
     9     10     11      1    1.0823e+02    8.3680e+02 ;    O3A - PA     - O1A   
     9     10     12      1    1.0823e+02    8.3680e+02 ;    O3A - PA     - O2A   
     9     10     13      1    1.0260e+02    3.7656e+02 ;    O3A - PA     - O5*   
    10     13     14      1    1.2050e+02    8.3680e+02 ;     PA - O5*    - C5*   
    11     10     12      1    1.1990e+02    1.1715e+03 ;    O1A - PA     - O2A   
    11     10     13      1    1.0823e+02    8.3680e+02 ;    O1A - PA     - O5*   
    12     10     13      1    1.0823e+02    8.3680e+02 ;    O2A - PA     - O5*   
    13     14     15      1    1.0950e+02    4.1840e+02 ;    O5* - C5*    - H50   
    13     14     16      1    1.0950e+02    4.1840e+02 ;    O5* - C5*    - H51   
    13     14     17      1    1.0950e+02    4.1840e+02 ;    O5* - C5*    - C4*   
    14     17     18      1    1.0950e+02    4.1840e+02 ;    C5* - C4*    - H40   
    14     17     19      1    1.0950e+02    4.1840e+02 ;    C5* - C4*    - O4*   
    14     17     36      1    1.0950e+02    3.3472e+02 ;    C5* - C4*    - C3*   
    15     14     16      1    1.0950e+02    2.9288e+02 ;    H50 - C5*    - H51   
    15     14     17      1    1.0950e+02    4.1840e+02 ;    H50 - C5*    - C4*   
    16     14     17      1    1.0950e+02    4.1840e+02 ;    H51 - C5*    - C4*   
    17     19     20      1    1.0950e+02    5.0208e+02 ;    C4* - O4*    - C1*   
    17     36     37      1    1.0950e+02    4.1840e+02 ;    C4* - C3*    - H30   
    17     36     38      1    1.0950e+02    4.1840e+02 ;    C4* - C3*    - O3*   
    17     36     40      1    1.0950e+02    3.3472e+02 ;    C4* - C3*    - C2*   
    18     17     19      1    1.0950e+02    4.1840e+02 ;    H40 - C4*    - O4*   
    18     17     36      1    1.0950e+02    4.1840e+02 ;    H40 - C4*    - C3*   
    19     17     36      1    1.0950e+02    4.1840e+02 ;    O4* - C4*    - C3*   
    19     20     21      1    1.0950e+02    4.1840e+02 ;    O4* - C1*    - H10   
    19     20     22      1    1.0950e+02    4.1840e+02 ;    O4* - C1*    - N9    
    19     20     40      1    1.0950e+02    4.1840e+02 ;    O4* - C1*    - C2*   
    20     22     23      1    1.2880e+02    5.8576e+02 ;    C1* - N9     - C8    
    20     22     35      1    1.2580e+02    5.8576e+02 ;    C1* - N9     - C4    
    20     40     36      1    1.0950e+02    3.3472e+02 ;    C1* - C2*    - C3*   
    20     40     41      1    1.0950e+02    4.1840e+02 ;    C1* - C2*    - H20   
    20     40     42      1    1.0950e+02    4.1840e+02 ;    C1* - C2*    - O2*   
    21     20     22      1    1.0950e+02    4.1840e+02 ;    H10 - C1*    - N9    
    21     20     40      1    1.0950e+02    4.1840e+02 ;    H10 - C1*    - C2*   
    22     20     40      1    1.0950e+02    4.1840e+02 ;     N9 - C1*    - C2*   
    22     23     24      1    1.2305e+02    4.1840e+02 ;     N9 - C8     - H80   
    22     23     25      1    1.1390e+02    5.8576e+02 ;     N9 - C8     - N7    
    22     35     26      1    1.0620e+02    5.8576e+02 ;     N9 - C4     - C5    
    22     35     34      1    1.2620e+02    5.8576e+02 ;     N9 - C4     - N3    
    23     22     35      1    1.0540e+02    5.8576e+02 ;     C8 - N9     - C4    
    23     25     26      1    1.0380e+02    5.8576e+02 ;     C8 - N7     - C5    
    24     23     25      1    1.2305e+02    4.1840e+02 ;    H80 - C8     - N7    
    25     26     27      1    1.3240e+02    5.8576e+02 ;     N7 - C5     - C6    
    25     26     35      1    1.1040e+02    5.8576e+02 ;     N7 - C5     - C4    
    26     27     28      1    1.2350e+02    5.8576e+02 ;     C5 - C6     - N6    
    26     27     31      1    1.1730e+02    5.8576e+02 ;     C5 - C6     - N1    
    26     35     34      1    1.2770e+02    5.8576e+02 ;     C5 - C4     - N3    
    27     26     35      1    1.1730e+02    5.2718e+02 ;     C6 - C5     - C4    
    27     28     29      1    1.2000e+02    4.1840e+02 ;     C6 - N6     - H60   
    27     28     30      1    1.2000e+02    4.1840e+02 ;     C6 - N6     - H61   
    27     31     32      1    1.1860e+02    5.8576e+02 ;     C6 - N1     - C2    
    28     27     31      1    1.1930e+02    5.8576e+02 ;     N6 - C6     - N1    
    29     28     30      1    1.2000e+02    2.9288e+02 ;    H60 - N6     - H61   
    31     32     33      1    1.1545e+02    4.1840e+02 ;     N1 - C2     - H2    
    31     32     34      1    1.2910e+02    5.8576e+02 ;     N1 - C2     - N3    
    32     34     35      1    1.1100e+02    5.8576e+02 ;     C2 - N3     - C4    
    33     32     34      1    1.1545e+02    4.1840e+02 ;     H2 - C2     - N3    
    36     38     39      1    1.0850e+02    4.6024e+02 ;    C3* - O3*    - H3'   
    36     40     41      1    1.0950e+02    4.1840e+02 ;    C3* - C2*    - H20   
    36     40     42      1    1.0950e+02    4.1840e+02 ;    C3* - C2*    - O2*   
    37     36     38      1    1.0950e+02    4.1840e+02 ;    H30 - C3*    - O3*   
    37     36     40      1    1.0950e+02    4.1840e+02 ;    H30 - C3*    - C2*   
    38     36     40      1    1.0950e+02    4.1840e+02 ;    O3* - C3*    - C2*   
    40     42     43      1    1.0850e+02    4.6024e+02 ;    C2* - O2*    - H2'   
    41     40     42      1    1.0950e+02    4.1840e+02 ;    H20 - C2*    - O2*   

[ dihedrals ] ; propers
; for gromacs 4.5 or higher, using funct 9
;    i      j      k      l   func   phase     kd      pn
     1      2      5      6      9     0.00   1.04600   3 ;    O1G-    PG-   O3B-    PB
     2      5      6      7      9     0.00   1.04600   3 ;     PG-   O3B-    PB-   O1B
     2      5      6      8      9     0.00   1.04600   3 ;     PG-   O3B-    PB-   O2B
     2      5      6      9      9     0.00   1.04600   3 ;     PG-   O3B-    PB-   O3A
     3      2      5      6      9     0.00   1.04600   3 ;    O2G-    PG-   O3B-    PB
     4      2      5      6      9     0.00   1.04600   3 ;    O3G-    PG-   O3B-    PB
     5      6      9     10      9     0.00   1.04600   3 ;    O3B-    PB-   O3A-    PA
     6      9     10     11      9     0.00   1.04600   3 ;     PB-   O3A-    PA-   O1A
     6      9     10     12      9     0.00   1.04600   3 ;     PB-   O3A-    PA-   O2A
     6      9     10     13      9     0.00   1.04600   3 ;     PB-   O3A-    PA-   O5*
     7      6      9     10      9     0.00   1.04600   3 ;    O1B-    PB-   O3A-    PA
     8      6      9     10      9     0.00   1.04600   3 ;    O2B-    PB-   O3A-    PA
     9     10     13     14      9     0.00   1.04600   3 ;    O3A-    PA-   O5*-   C5*
     9     10     13     14      9     0.00   5.02080   2 ;    O3A-    PA-   O5*-   C5*
    10     13     14     15      9     0.00   1.60387   3 ;     PA-   O5*-   C5*-   H50
    10     13     14     16      9     0.00   1.60387   3 ;     PA-   O5*-   C5*-   H51
    10     13     14     17      9     0.00   1.60387   3 ;     PA-   O5*-   C5*-   C4*
    10     13     14     17      9   180.00  16.52680   1 ;     PA-   O5*-   C5*-   C4*
    11     10     13     14      9     0.00   2.30120   3 ;    O1A-    PA-   O5*-   C5*
    11     10     13     14      9     0.00   3.34720   2 ;    O1A-    PA-   O5*-   C5*
    12     10     13     14      9     0.00   2.30120   3 ;    O2A-    PA-   O5*-   C5*
    12     10     13     14      9     0.00   3.34720   2 ;    O2A-    PA-   O5*-   C5*
    13     14     17     18      9     0.00   0.00000   0 ;    O5*-   C5*-   C4*-   H40
    13     14     17     18      9     0.00   1.04600   1 ;    O5*-   C5*-   C4*-   H40
    13     14     17     19      9     0.00   0.60250   3 ;    O5*-   C5*-   C4*-   O4*
    13     14     17     19      9     0.00   4.91620   2 ;    O5*-   C5*-   C4*-   O4*
    13     14     17     36      9     0.00   0.65084   3 ;    O5*-   C5*-   C4*-   C3*
    14     17     19     20      9     0.00   1.60247   3 ;    C5*-   C4*-   O4*-   C1*
    14     17     19     20      9   180.00   0.41840   2 ;    C5*-   C4*-   O4*-   C1*
    14     17     36     37      9     0.00   0.65084   3 ;    C5*-   C4*-   C3*-   H30
    14     17     36     38      9     0.00   0.65084   3 ;    C5*-   C4*-   C3*-   O3*
    14     17     36     40      9     0.00   0.75312   3 ;    C5*-   C4*-   C3*-   C2*
    14     17     36     40      9   180.00   0.83680   1 ;    C5*-   C4*-   C3*-   C2*
    14     17     36     40      9   180.00   1.04600   2 ;    C5*-   C4*-   C3*-   C2*
    15     14     17     18      9     0.00   0.65084   3 ;    H50-   C5*-   C4*-   H40
    15     14     17     19      9     0.00   0.00000   0 ;    H50-   C5*-   C4*-   O4*
    15     14     17     19      9     0.00   1.04600   1 ;    H50-   C5*-   C4*-   O4*
    15     14     17     36      9     0.00   0.65084   3 ;    H50-   C5*-   C4*-   C3*
    16     14     17     18      9     0.00   0.65084   3 ;    H51-   C5*-   C4*-   H40
    16     14     17     19      9     0.00   0.00000   0 ;    H51-   C5*-   C4*-   O4*
    16     14     17     19      9     0.00   1.04600   1 ;    H51-   C5*-   C4*-   O4*
    16     14     17     36      9     0.00   0.65084   3 ;    H51-   C5*-   C4*-   C3*
    17     19     20     21      9     0.00   1.60387   3 ;    C4*-   O4*-   C1*-   H10
    17     19     20     22      9     0.00   1.60247   3 ;    C4*-   O4*-   C1*-    N9
    17     19     20     22      9     0.00   2.71960   2 ;    C4*-   O4*-   C1*-    N9
    17     19     20     40      9     0.00   1.60247   3 ;    C4*-   O4*-   C1*-   C2*
    17     19     20     40      9   180.00   0.41840   2 ;    C4*-   O4*-   C1*-   C2*
    17     36     38     39      9     0.00   0.66944   3 ;    C4*-   C3*-   O3*-   H3'
    17     36     38     39      9     0.00   1.04600   1 ;    C4*-   C3*-   O3*-   H3'
    17     36     40     20      9     0.00   0.75312   3 ;    C4*-   C3*-   C2*-   C1*
    17     36     40     20      9   180.00   0.83680   1 ;    C4*-   C3*-   C2*-   C1*
    17     36     40     20      9   180.00   1.04600   2 ;    C4*-   C3*-   C2*-   C1*
    17     36     40     41      9     0.00   0.65084   3 ;    C4*-   C3*-   C2*-   H20
    17     36     40     42      9     0.00   0.65084   3 ;    C4*-   C3*-   C2*-   O2*
    18     17     19     20      9     0.00   1.60387   3 ;    H40-   C4*-   O4*-   C1*
    18     17     36     37      9     0.00   0.65084   3 ;    H40-   C4*-   C3*-   H30
    18     17     36     38      9     0.00   0.00000   0 ;    H40-   C4*-   C3*-   O3*
    18     17     36     38      9     0.00   1.04600   1 ;    H40-   C4*-   C3*-   O3*
    18     17     36     40      9     0.00   0.65084   3 ;    H40-   C4*-   C3*-   C2*
    19     17     36     37      9     0.00   0.00000   0 ;    O4*-   C4*-   C3*-   H30
    19     17     36     37      9     0.00   1.04600   1 ;    O4*-   C4*-   C3*-   H30
    19     17     36     38      9     0.00   0.60250   3 ;    O4*-   C4*-   C3*-   O3*
    19     17     36     38      9     0.00   4.91620   2 ;    O4*-   C4*-   C3*-   O3*
    19     17     36     40      9     0.00   0.65084   3 ;    O4*-   C4*-   C3*-   C2*
    19     20     22     23      9     0.00   0.00000   0 ;    O4*-   C1*-    N9-    C8
    19     20     22     23      9     0.00  10.46000   1 ;    O4*-   C1*-    N9-    C8
    19     20     22     35      9     0.00   0.00000   0 ;    O4*-   C1*-    N9-    C4
    19     20     40     36      9     0.00   0.65084   3 ;    O4*-   C1*-   C2*-   C3*
    19     20     40     41      9     0.00   0.00000   0 ;    O4*-   C1*-   C2*-   H20
    19     20     40     41      9     0.00   1.04600   1 ;    O4*-   C1*-   C2*-   H20
    19     20     40     42      9     0.00   0.60250   3 ;    O4*-   C1*-   C2*-   O2*
    19     20     40     42      9     0.00   4.91620   2 ;    O4*-   C1*-   C2*-   O2*
    20     19     17     36      9     0.00   1.60247   3 ;    C1*-   O4*-   C4*-   C3*
    20     19     17     36      9   180.00   0.41840   2 ;    C1*-   O4*-   C4*-   C3*
    20     22     23     24      9   180.00   7.11280   2 ;    C1*-    N9-    C8-   H80
    20     22     23     25      9   180.00   7.11280   2 ;    C1*-    N9-    C8-    N7
    20     22     35     26      9   180.00   6.90360   2 ;    C1*-    N9-    C4-    C5
    20     22     35     34      9   180.00   6.90360   2 ;    C1*-    N9-    C4-    N3
    20     40     36     37      9     0.00   0.65084   3 ;    C1*-   C2*-   C3*-   H30
    20     40     36     38      9     0.00   0.65084   3 ;    C1*-   C2*-   C3*-   O3*
    20     40     42     43      9     0.00   0.66944   3 ;    C1*-   C2*-   O2*-   H2'
    20     40     42     43      9     0.00   1.04600   1 ;    C1*-   C2*-   O2*-   H2'
    21     20     22     23      9     0.00   0.00000   0 ;    H10-   C1*-    N9-    C8
    21     20     22     35      9     0.00   0.00000   0 ;    H10-   C1*-    N9-    C4
    21     20     40     36      9     0.00   0.65084   3 ;    H10-   C1*-   C2*-   C3*
    21     20     40     41      9     0.00   0.65084   3 ;    H10-   C1*-   C2*-   H20
    21     20     40     42      9     0.00   0.65084   3 ;    H10-   C1*-   C2*-   O2*
    22     20     40     36      9     0.00   0.65084   3 ;     N9-   C1*-   C2*-   C3*
    22     20     40     41      9     0.00   0.65084   3 ;     N9-   C1*-   C2*-   H20
    22     20     40     42      9     0.00   0.65084   3 ;     N9-   C1*-   C2*-   O2*
    22     23     25     26      9   180.00  41.84000   2 ;     N9-    C8-    N7-    C5
    22     35     26     25      9   180.00  22.80280   2 ;     N9-    C4-    C5-    N7
    22     35     26     27      9   180.00  22.80280   2 ;     N9-    C4-    C5-    C6
    22     35     34     32      9   180.00  17.36360   2 ;     N9-    C4-    N3-    C2
    23     22     20     40      9     0.00   0.00000   0 ;     C8-    N9-   C1*-   C2*
    23     22     35     26      9   180.00   6.90360   2 ;     C8-    N9-    C4-    C5
    23     22     35     34      9   180.00   6.90360   2 ;     C8-    N9-    C4-    N3
    23     25     26     27      9   180.00  10.66920   2 ;     C8-    N7-    C5-    C6
    23     25     26     35      9   180.00  10.66920   2 ;     C8-    N7-    C5-    C4
    24     23     22     35      9   180.00   7.11280   2 ;    H80-    C8-    N9-    C4
    24     23     25     26      9   180.00  41.84000   2 ;    H80-    C8-    N7-    C5
    25     23     22     35      9   180.00   7.11280   2 ;     N7-    C8-    N9-    C4
    25     26     27     28      9   180.00  14.64400   2 ;     N7-    C5-    C6-    N6
    25     26     27     31      9   180.00  14.64400   2 ;     N7-    C5-    C6-    N1
    25     26     35     34      9   180.00  22.80280   2 ;     N7-    C5-    C4-    N3
    26     27     28     29      9   180.00  10.04160   2 ;     C5-    C6-    N6-   H60
    26     27     28     30      9   180.00  10.04160   2 ;     C5-    C6-    N6-   H61
    26     27     31     32      9   180.00  20.08320   2 ;     C5-    C6-    N1-    C2
    26     35     34     32      9   180.00  17.36360   2 ;     C5-    C4-    N3-    C2
    27     26     35     34      9   180.00  22.80280   2 ;     C6-    C5-    C4-    N3
    27     31     32     33      9   180.00  28.45120   2 ;     C6-    N1-    C2-    H2
    27     31     32     34      9   180.00  28.45120   2 ;     C6-    N1-    C2-    N3
    28     27     26     35      9   180.00  14.64400   2 ;     N6-    C6-    C5-    C4
    28     27     31     32      9   180.00  20.08320   2 ;     N6-    C6-    N1-    C2
    29     28     27     31      9   180.00  10.04160   2 ;    H60-    N6-    C6-    N1
    30     28     27     31      9   180.00  10.04160   2 ;    H61-    N6-    C6-    N1
    31     27     26     35      9   180.00  14.64400   2 ;     N1-    C6-    C5-    C4
    31     32     34     35      9   180.00  28.45120   2 ;     N1-    C2-    N3-    C4
    33     32     34     35      9   180.00  28.45120   2 ;     H2-    C2-    N3-    C4
    35     22     20     40      9     0.00   0.00000   0 ;     C4-    N9-   C1*-   C2*
    36     40     42     43      9     0.00   0.66944   3 ;    C3*-   C2*-   O2*-   H2'
    36     40     42     43      9     0.00   1.04600   1 ;    C3*-   C2*-   O2*-   H2'
    37     36     38     39      9     0.00   0.69733   3 ;    H30-   C3*-   O3*-   H3'
    37     36     40     41      9     0.00   0.65084   3 ;    H30-   C3*-   C2*-   H20
    37     36     40     42      9     0.00   0.00000   0 ;    H30-   C3*-   C2*-   O2*
    37     36     40     42      9     0.00   1.04600   1 ;    H30-   C3*-   C2*-   O2*
    38     36     40     41      9     0.00   0.00000   0 ;    O3*-   C3*-   C2*-   H20
    38     36     40     41      9     0.00   1.04600   1 ;    O3*-   C3*-   C2*-   H20
    38     36     40     42      9     0.00   0.60250   3 ;    O3*-   C3*-   C2*-   O2*
    38     36     40     42      9     0.00   4.91620   2 ;    O3*-   C3*-   C2*-   O2*
    39     38     36     40      9     0.00   0.66944   3 ;    H3'-   O3*-   C3*-   C2*
    39     38     36     40      9     0.00   1.04600   1 ;    H3'-   O3*-   C3*-   C2*
    41     40     42     43      9     0.00   0.69733   3 ;    H20-   C2*-   O2*-   H2'

[ dihedrals ] ; impropers
; treated as propers in GROMACS to use correct AMBER analytical function
;    i      j      k      l   func   phase     kd      pn
    22     26     35     34      4   180.00   0.00000   2 ;     N9-    C5-    C4-    N3
    24     22     23     25      4   180.00   4.60240   2 ;    H80-    N9-    C8-    N7
    25     27     26     35      4   180.00   0.00000   2 ;     N7-    C6-    C5-    C4
    26     28     27     31      4   180.00   4.60240   2 ;     C5-    N6-    C6-    N1
    27     29     28     30      4   180.00   4.18400   2 ;     C6-   H60-    N6-   H61
    33     31     32     34      4   180.00   4.60240   2 ;     H2-    N1-    C2-    N3
    35     23     22     20      4   180.00   4.18400   2 ;     C4-    C8-    N9-   C1*

HI Josh,

Thanks a lot. So this topology goes with amber99sb-star-ildn.ff forcefield for Protein? Just to be sure.

regards,
satti